1. Technical Field
The present invention relates to a cutter drive mechanism and to a cutter that cut sheet media by reciprocally moving a cutter blade. The invention also relates to a printer having the cutter.
2. Related Art
A printer with a cutter is described in JP-A-H10-217182. The cutter in JP-A-H10-217182 has cutter blade drive mechanism that drives a cutter blade reciprocally between a forward position where the recording paper is cut and a retracted position separated from the forward position. The cutter blade drive mechanism has a drive motor, two cutter drive gears to which drive power is transferred from the drive motor, and a guide that guides the movable knife in the forward/back direction. The two cutter drive gears are arranged in a perpendicular direction perpendicular to the forward/back direction of motion (or travel) of the movable knife with their axes of rotation perpendicular to the plane of motion of the movable knife. The two cutter drive gears mesh together and rotate synchronously. Each cutter drive gear has a drive pin disposed to a position offset from the center of the end face. Oval holes with the long axis extending in the perpendicular direction are formed in the movable knife, and the drive pins of the cutter drive gears are inserted in these holes.
When the two cutter drive gears turn by the drive power from the drive motor, the drive pins move in the forward/back direction of the movable knife while moving in the perpendicular direction inside the oval holes. The drive pins therefore contact the sides of the oval holes and move the movable knife in the forward/back direction. When the cutter drive gears turn one revolution, the movable knife travels round trip to the forward position overlapping the fixed knife and then back to the retracted position forming a gap between the movable knife and the fixed knife. With the cutter blade drive mechanism described in JP-A-H10-217182, the drive motor stops after the movable knife returns from the forward position to the retracted position.
If the position where the drive motor stops varies with the cutter blade drive mechanism described in JP-A-H10-217182, the position of the movable knife will be offset from the retracted position by the amount of deviation in the position of the drive motor. If the movable knife returned to the retracted position is thus offset to the forward position side of the retracted position, and the movable knife is normally covered by a cover when at the retracted position, the cutting edge of the movable knife may be dangerously exposed from the cover. The stroke of the movable knife must therefore be increased so that the movable knife is positioned where it will be covered by the cover even when the position where the drive motor stops varies. Increasing the stroke of the movable knife may increase the size of the device, however.